B+Tree Database

A compact, educational database engine written in C, demonstrating key concepts of relational databases using a disk-backed B+Tree data structure.

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Features

• Multi-Table Support: Create and manage multiple tables with named columns.
• B+Tree Indexing: Fast lookups, inserts, and range queries using a balanced B+Tree structure.
• Disk-based Persistence: Data is stored on disk in pages, supporting durability and efficient I/O.
• Flexible Schemas: Support for integer and fixed-size text columns, plus primary key constraints.
• SQL-like CLI: Interactive command shell for creating tables, inserting records, and querying data.
• Meta-Commands: View existing tables, inspect table B+Tree structure, and clean exit.

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Getting Started

Build

Make sure you have gcc installed. Run:

make

This produces the executable: bplus_db

Usage

To create or open a database:

./bplus_db mydatabase.db

You’ll enter the CLI prompt. Available commands:

CREATE TABLE <table> <num_columns>          # Create a new table
INSERT INTO <table> VALUES <val1> ...       # Insert a record
INSERT <table> <val1> ...                   # Insert (short form)
SELECT * FROM <table>                       # Display all records
SELECT <col1> <col2> FROM <table>           # Display specific columns
SELECT * FROM <table> WHERE <col> <op> <val> # Filter results
  Operators: =, >, <, >=, <=, BETWEEN x AND y
.tables                                     # List all tables
.btree <table>                              # Print B+Tree structure
.exit                                       # Quit the CLI

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Directory Structure

• src/ — Source code for all subsystems: CLI, B+Tree, table, pager.
• include/ — Header files for all modules.
• Makefile — Build system.

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Technical Overview

• B+Tree Index: Used for primary key and row organization.
• Pager: Loads/saves 4KB pages to disk, supporting a large database file.
• Table/Schema Management: Flexible table definitions—set column name/type/PK when created.
• Row Serialization: Efficient binary layout for storage/retrieval.
• Write-Ahead Log (WAL): For crash safety (if enabled).

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Example Session

$ ./bplus_db example.db
Multi-Table B+Tree Database with SQL-like syntax
Commands:
  CREATE TABLE <table> <num_columns>
  INSERT <table> <val1> ...
  SELECT * FROM <table>
  .tables
  .btree <table>
  .exit

db > CREATE TABLE users 3
Column 1: id int PRIMARY KEY
Column 2: name text 32
Column 3: age int
Table 'users' created successfully
PRIMARY KEY: id (fast lookups enabled)
db > INSERT users 1 Alice 30
Executed.
db > SELECT * FROM users
Key: 1 | id: 1, name: Alice, age: 30
(1 rows matched)
[Optimized: B+tree range scan]
db > .exit

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Learning Goals

• Understand B+Tree internals
• See how persistence, schemas, and indexes are built from scratch
• Appreciate the mechanics behind relational databases

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Author

This project is intended for learning and experimentation.